Artist is to become a writer (8)
I believe the answer is:
satirist
'a writer' is the definition.
(satirist matches up with the definition a writer)
'artist is to become' is the wordplay.
'to become' indicates an anagram.
'artist'+'is'='artistis'
'artistis' with letters rearranged gives 'SATIRIST'.
(Other definitions for satirist that I've seen before include "Biting comic" , "Humorist who uses ridicule, irony and sarcasm" , "Pope, say" , "a ridiculous guy" , "comedian" .)